So you’re pretty sure you’ve ovulated, and you did your best to get pregnant – what now?
In the ‘average’ 28 day cycle, menstruation occurs on Day 1 and ovulation occurs after this at around Day 14.
Many women get confused by the ‘Day 14’ terminology and assume that ovulation occurs fourteen days after menstruation has ended, when (assuming an ‘average’ 5 days of menstruation) it is more likely to be around nine days after menstruation has finished.
It is usually around fourteen days after ovulation, before menstruation starts again – however very few women have an ‘average’ cycle.
The time after ovulation is known as the ‘luteal phase’ and is the longest-lasting phase of the menstrual cycle.
It is only possible to get pregnant for a short period of time after ovulation.
After ovulation – when the egg is released from the follicle – there is a period of between 12 and 48 hours when the egg is available to be fertilised by a mature sperm.
Sperm can last for up to five days inside a woman’s body, sustained by the cervical mucus – so often, just after ovulation, sperm already waiting in the fallopian tubes will fertilise the egg after it has just been released.
Healthy, active sperm take around six hours after ejaculation to swim through the cervix and the uterus into the fallopian tube to meet a waiting egg, so for one to two days after ovulation, it is still possible to fall pregnant.
In any one menstrual cycle, there will be just one fertile period. As levels of FSH (follicular stimulating hormone) rise, a number of follicles develop in your ovaries, but usually just one is released.
Because ovulation is triggered by a particular combination of hormones that rises and falls over the normal menstrual cycle, eggs can only be released from the ovaries during the 24-hour period when the ovulation-promoting hormones are at their peak.
A pregnancy with fraternal twins results from two eggs being released from two different follicles, within the same 24-hour period.
Between one and three percent of all births are fraternal twins. However, advances in ultrasound technology have led to research into the ?vanishing twin syndrome.’
It is now thought that up to one in eight pregnancies may involve the very early fertilisation of more than one egg, but less than half of the second embryos will survive for more than a few weeks after ovulation. If the embryo does not survive, it is reabsorbed by the body.
After ovulation, hormone levels decline and you must go through a feedback cycle which triggers menstruation before you ovulate again.
For the next eight days or so after ovulation, the same events occur in your body whether the egg has been fertilised or not.
The follicle which released the egg grows larger and turns into a gland-like structure called the ‘corpus luteum.’ After this, it then starts to produce the hormone progesterone, which causes the lining of the uterus (the endometrium) to grow thick and become covered with mucous that is produced by glands within the endometrium.
After ovulation, if you are not pregnant, within 48 hours, the egg moves along the fallopian tubes, disintegrates and is absorbed back into the body.
The corpus luteum survives and continues to produce progesterone for around 12 to 14 days. After this, it dies (unless it receives the hCG hormone released from an embryo).
The level of progesterone in the body drops and the endometrium responds by shutting off its arteries, preventing blood from flowing to and from the surface of the uterine lining.
The blood that is already in the lining then pools lower in the uterus and the mucous-covered uterine lining, deprived of oxygen, dies back, the blood and lining seep into the vagina, so menstruation occurs and the cycle begins again.
After ovulation and until menstruation, your basal body temperature remains about 0.5 degrees Celsius higher. Your cervical mucus becomes less slippery and more sticky or creamy in consistency.
The moment that one of the millions of sperm enters the outer surface of the egg, the egg’s coating changes so no other sperm can enter, the sperm and egg combine and form a ‘zygote.’
After this, the zygote takes around five days to travel down the fallopian tube, with cells dividing and eventually forming a ‘blastocyst.’
Around eight to ten days after fertilisation, the blastocyst implants into the wall of the uterus.
Before implantation, there’s not a lot of change going on in your body, which behaves just as it would if you weren’t pregnant.
But after ovulation and then implantation, the fun begins. Sometimes there is a slight spotting or bleeding just after implantation – which some women mistake for a period.
But when the blastocyst attaches to the endometrium, becoming an embryo, various hormones are released which thicken the endometrium and seal the cervix with a plug of mucous.
The embryo and placenta develop separately. After implantation, the placenta produces the hormone human chorionic gonadotropin (hCG). Within a few days, the level of hCG is able to be detected in urine, using a pregnancy test.
By Fran Molloy, journalist and mum of four